There is a demand for portable telecommunication devices such as cellular telephones, Global Positioning System (GPS) enabled devices, Wi-Fi® and Bluetooth® enabled portable devices, Global System for Mobile Communications (GSM) enabled portable devices, Wideband Code Division Multiplex (WCDMA) enabled portable devices, etc. As the demand increases for portable telecommunication devices with a variety of communication features, manufacturers are now combining and integrating many of these devices. For example, cellular phones are integrated with GPS receivers for providing position information.
As an increasing number of telecommunication devices are integrated together, each receiver's interference rejection to out-of-band signals may become more important. For example, higher order nonlinearities may cause out-of-band interferers to translate to an in-band spectrum of a receiver, which may result in signal degradation or a loss of signal reception. WCDMA interference, for example, may be a concern for low intermediate frequency (IF) receivers, because any second order nonlinearities in the receiver may result in the WCDMA signal being folded into the IF band.
Any higher order nonlinearities may generate spurious signals. For example, second order modulation (IM2) products may be generated when an AM signal encounters a second-order nonlinearity in the mixer circuit. One performance measure related to IM2 products is the second order intercept (IP2), which may be used to quantify the second-order distortion in the receiver. IP2 performance in an integrated circuit receiver is typically limited by device mismatch and device nonlinearity. Accordingly, the IP2 performance may be improved by directly reducing device mismatch and device nonlinearities (to minimize IM2 products) without the aid of operational circuit adjustments. This methodology, however, may require additional area on the chip, may increase the complexity, reduce the yield and may increase the power consumption.